Electromagnetic Field Analysis for Circularly Polarized Light at the Apex of the Near-Field Optical Probe

Abstract

In this study, a finite-difference time-domain method is applied to analyze the propagation of circularly polarized light in a tapered near-field optical-fiber probe with a small aperture. A simulated model of the probe with an aperture diameter of 100 nm was designed, and the electric field distribution and orientation of its vector for circularly polarized light were calculated in the time domain. The result of the simulation shows that the circularly polarized light state was maintained after passing through the small aperture, albeit with a slight modification due to the field enhancement caused by the metallic edge at the aperture. The phase retardation between the orthogonal components of the circular polarization at the aperture plane was found to increase slightly along the radial direction away from the center of the aperture. Also, the retardation of an anisotropic sample in the near field was calculated using the orthogonal components of the illuminated circular polarization.